What is G-force: Definition and 61 Discussions

The gravitational force equivalent, or, more commonly, g-force, is a measurement of the type of force per unit mass – typically acceleration – that causes a perception of weight, with a g-force of 1 g (not gram in mass measurement) equal to the conventional value of gravitational acceleration on Earth, g, of about 9.8 m/s2. Since g-forces indirectly produce weight, any g-force can be described as a "weight per unit mass" (see the synonym specific weight). When the g-force is produced by the surface of one object being pushed by the surface of another object, the reaction force to this push produces an equal and opposite weight for every unit of an object's mass. The types of forces involved are transmitted through objects by interior mechanical stresses. Gravitational acceleration (except certain electromagnetic force influences) is the cause of an object's acceleration in relation to free fall.The g-force experienced by an object is due to the vector sum of all non-gravitational and non-electromagnetic forces acting on an object's freedom to move. In practice, as noted, these are surface-contact forces between objects. Such forces cause stresses and strains on objects, since they must be transmitted from an object surface. Because of these strains, large g-forces may be destructive.
Gravity acting alone does not produce a g-force, even though g-forces are expressed in multiples of the free-fall acceleration of standard gravity. Thus, the standard gravitational force at the Earth's surface produces g-force only indirectly, as a result of resistance to it by mechanical forces. It is these mechanical forces that actually produce the g-force on a mass. For example, a force of 1 g on an object sitting on the Earth's surface is caused by the mechanical force exerted in the upward direction by the ground, keeping the object from going into free fall. The upward contact force from the ground ensures that an object at rest on the Earth's surface is accelerating relative to the free-fall condition. (Free fall is the path that the object would follow when falling freely toward the Earth's center). Stress inside the object is ensured from the fact that the ground contact forces are transmitted only from the point of contact with the ground.
Objects allowed to free-fall in an inertial trajectory under the influence of gravitation only feel no g-force, a condition known as zero-g (which means zero g-force). This is demonstrated by the "zero-g" conditions inside an elevator falling freely toward the Earth's center (in vacuum), or (to good approximation) conditions inside a spacecraft in Earth orbit. These are examples of coordinate acceleration (a change in velocity) without a sensation of weight. The experience of no g-force (zero-g), however it is produced, is synonymous with weightlessness.
In the absence of gravitational fields, or in directions at right angles to them, proper and coordinate accelerations are the same, and any coordinate acceleration must be produced by a corresponding g-force acceleration. An example here is a rocket in free space, in which simple changes in velocity are produced by the engines and produce g-forces on the rocket and passengers.

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  1. H

    G-force to pressure relationship inside a shock wave

    I need some help understanding shock waves, particularly the units of measure related to their pressure. Shock waves are frequently quantified as multiples of G, the gravitational constant. I need to understand how the G measurements related to the instantaneous pressure within the wave as...
  2. D

    I G-force centrifuge mounted on opposite rotating platform

    Query - does a centrifuge spinning to create X g-force, mounted on a platform that is rotating the the same rpm's the opposite direction, negate the g-force? Or does the g-force stay the same but from an outside perspective the centrifuge appears stationary?
  3. rudransh verma

    B A question from Resnik about g-force

    Suppose there is one force gravitational force ##\vec{f_g}##. We can relate this downward force and downward acceleration with Newton sec law. This law can be written as ##F_{net,y}=ma_y## which becomes $$-F_g=m(-g)$$ or $$F_g=mg$$ $$\vec{F_g}=-F_g \hat j=-mg \hat j=m\vec g$$. Is it right...
  4. S

    I What are the effects of Buoyancy & G-force combined in this scenario?

    Hi all, I am trying to get it straight in my head how the interactions would work with a person (or accelerometer, for simplicity) suspended in a fluid, which is itself in a capsule which is then accelerated. Let's say with a rocket, on a linear track, to avoid any circular motion dynamics...
  5. M

    Finding the 'g-force' of a decelerating falling mass.

    Hey all, I need a reality check and verification on some work I have been doing. I feel as though I might be too close to the problem now and am missing something about this. It's also been a few years since I studied physics at University, so I'm a little rusty. Problem: An initially...
  6. J

    G-force experienced by a jumper, using a DE

    We are given that ##v' = \frac{1}{10}v^2 - g##. I tried using implicit differentiation so that ##v'' = \frac{1}{5}vv' = \frac{1}{5}v(\frac{1}{10}v^2-g)## and set this equal to 0. Hence we have 3 critical points, at ##v= 0##, and ##v = \pm \sqrt{10g}##. Calculating ##v''(0)=-120##, we know the...
  7. E

    G-force diagram on a roller coaster?

    So, while we were going up the track, the z-direction gforce seemed to go up. It went from -1 to about -0.6. The x-direction seemed to be around 0, more or less? All x values were under 0.177. The y-direction decreased, more or less, from -0.4 to -0.9. I think if I understand how the force...
  8. solarmidnightrose

    B Understanding G-Force: x,y and z Components Explained

    I've been to the amusement park recently, and one day I decided to use an app (Physics Toolbox), to collect some data. I downloaded the data, and it gave it to me in a .csv format. This table of data showed that there were x,y and z values for G-Force. I don't understand how G-Force has x,y...
  9. gibberingmouther

    G-Force Tolerance and Heart Rate

    This is about my tabletop game again. Hypothetically speaking, if your heart rate was faster because of an "altered time rate" - anywhere from X2 to significantly more than that times the normal time rate - would that increase your g force tolerance? I'm speaking mainly about a g-force...
  10. D

    Having Trouble Finding G-Force of an Impact -- Details in post

    Hey guys first post on here for me. Graduated with a BS in Civil Engineering and working full time. Have a problem on my desk that myself and many coworkers are trying to figure out and would like some assistance as we haven't done anything like this in years. Not sure if we even have the...
  11. M

    Getting the init. velocity given G-force?

    Homework Statement If an object is horizontally pushed with a g-force of 2.6 (imagine a cart with no friction on the wheels being in constant contact with a pusher being pushed for 1600 ft at that g-force and then stops but the cart keeps moving) what is the initial velocity right after it's...
  12. Paul Nefdt

    B G-Force Displacement -- Is it possible?

    Hi Guys I was wondering if the effects of G-Forces can be displaced?? e.g if a body or object is placed in water (more like encapsulated in water) & is then subjected to tremendous acceleration very quickly, would there still be a G-Force effect on the object inside the water?
  13. I

    I Question about a g-force meter

    I few weeks ago I purchased a new Camaro with a Head's Up Display and among the data presented is a g-force meter. The meter does not show acceleration or deceleration; instead it is strictly lateral. Yesterday I entered a long and banked on-ramp to a freeway and the g-force meter reached...
  14. K

    Flow rate of water from thin tubes under high g-force

    Hi guys, I was wondering if you could help me with something. I work in the paper industry with what is called a suction roll. The roll has a rotating perforated steel cylinder with a stationary vacuum box on the inside and as the wet paper web travels over the surface of the roll, the vacuum...
  15. A

    Why do Jet fighter pilots experience a greater G-force?

    Hi! I'm a high school student, aspiring to pursue a career in Astronautical Engineering. I always try and ponder on questions about everyday aerodynamics and physics. So, here's a question from you from an aspiring scholar. It is known that, at high velocities, pilots in super-sonic jet...
  16. H

    G-Force Definition: Acc & Weightlessness

    I am having considerable difficulty in finding a precise definition of g-force. My understanding is that it is the acceleration an object would undergo due to just the non-gravitational and non-electromagnetic forces acting on the object. A corollary of this is that an object experiences zero...
  17. H

    Calculate speed of object given g-force

    Hello. I am new to this website and am not looking for homework help. In fact I have no background in physics whatsoever. I am looking for the speed necessary to cause a specific g-force rating of 5.22 on an object weighing in at 11, 245 lbs and the distance covered would be approximately 1...
  18. O

    G-Force between 2 objects, find time?

    Homework Statement Spaceship mass=450000kg Initial Velocity= 300m/s y + 400m/s z Asteroid mass = 2000kg Initial Velocity= -100m/s y - 50m/s z Speed after 498m/s Question: If the force between the objects is 5000N, how long will it take for spaceship to capture the asteroid? (Assume...
  19. M

    Calculating Cyclic Energy from Acceleration (Relative)

    Hello, I am looking at relating two situations under which cyclic energy is applied to a material. Condition 1: A material has been subjected to a force of 1G at 0.1Hz for 47 days. Condition 2: The same material has been subjected to a force of 4.5G at 60Hz for 3600Seconds. Is it possible to...
  20. C

    Is Impact Force Equal to G-Force in Newtons?

    Hi, I am dropping an object of mass m at different heights on another body. From the accelerometer I have I can get the g-force and then convert it into Newtons. What I am wondering, is the force converted into Newtons equal to the impact force the mass exerts on the body?
  21. Sterling07

    Calculating G-Force on Gravitron Ride

    Homework Statement i have a question where i need to calculate the g's experienced by people on a carnival ride called the "gravitron" the ride simply spins riders around in a circle. i have calculated Vc(centripetal velocity) to be 20.9439m/s and the radius is 3.0 meters... how would i...
  22. DocZaius

    What is G-Force Before Engines Turn On?

    I was looking at this graph and wondering what the value of the graph would be before the engines turn on. Should it be 1 g-force or 0 g-force? (the "force" in g-force being a misnomer as it is a measure of acceleration, not force) Below are arguments for each: Why it should be 1 g-force: We...
  23. M

    Help calculating the G-Force in a corner

    Hi, I recently got a red light ticket for supposedly running a left turn and I wanted to try to fight the ticket. The officer told me I took the turn at 40-45 mph and then immediately wrote down 45-50 mph on the ticket. In one of my arguments, I want to try to prove that my car can't execute a...
  24. L

    Measuring punching G-Force on a Pendulum

    I am building a machine for my martial arts club so that I can have a bit of fun and measure the speed and reaction times of my club mates. The design that I feel would yield the most reliable and accurate results would be to mount an upside down 'pendulum' on a frame. At the head of the...
  25. A

    What is the relationship between weight and g-force in determining F?

    Hi. Can you clarify for me the equation for g-force below: F= ma + mg I got this equation from my lecturer. He asked the class to determine how was the formula above formulated. But this is not a homework. Is the equation above true for g-force? If it's true, how does...
  26. M

    Difference between G-force and Grms

    I am currently doing a vibration analysis using a random vibration machine which gives Grms value based on Power Spectral Density (PSD) plot using Fast Fourier transform(FFT). Before I ran the test on my specimen, I tried to characterise the vibration using a DDSR board (accelerometer)...
  27. E

    Calculate approximately G-force applied on Car shock absorber

    I have to do some dataacquisition from a car with some accelerometers. 4 accelerometers is placed on the wheels before the shock absorber. And i need to calculate the maximum applied G-force on the accelerometers. Just an approximately value, not taking in account the type of wheel...
  28. C

    G-force of wind on a persons body.

    After doing some work with a painter friend we were coming home and I put my arm outside of the window as we were going 70 miles an hour. Wondering what the g-forces would be on my arms and hand? Thank you
  29. V

    Sci-fi question: Would the power required to sustain a g-force during acceleration be

    On the way into work this morning, happily reading my book (Leviathan Wakes, would suggest it to any sci-fi space opera fan) and there was a passage that read along the lines “they reduced acceleration to sustain a 1g force during the meal” or something along those lines. Its something you...
  30. S

    Calculate G-Force: How to Measure Gravity's Force

    How do you calculate G-Force? I know that one g is the force gravity exerts on a particular mass (I think). But how exactly do you figure it out, particularly with objects spinning in a circle, like a merry-go-round?
  31. S

    G-Force and (possibly) Centrifugal force applied to the rotation of a car

    1. I'm in my first year of physics, and the end-of-year project is a bit of a doozy: find two examples of misapplied physics in movies and explain how it's wrong. For my first example, I chose a scene from the movie "The Iron Giant," in which the Giant picks up a car with Hogarth, our child...
  32. J

    What is the degree of maximum g-force in a car's turn?

    I am interested in a car's transition from zero cornering force (just before entering a corner) to maximum cornering force (somewhere in the corner). In particular, I would like to know how far into the corner it takes (in degrees) for this transition to happen. Assume a car is capable of...
  33. G

    Is someone know how to calculate vertical G-force

    Hi, I eager want to know about how to calculate the vertical G-force.I have some ideas but I do not if it is right or not.I just calculate the acceleration first,then use a/9.8 kg/N or m/s^2. Is this formula right or not?Is someone can tell me? Thanks in advance.
  34. S

    Acceleration of a plane and the g-force

    Acceleration of a plane and the "g-force" Homework Statement Steam catapults are used to launch aircraft. During the launch of a F/A-18 jet (mass: 16,770 kg) the catapult accelerates from 0 to 250 km/hr within 76m of deck length. Calculate the force produced by the catapult, the acceleration...
  35. J

    Calculating Rotational Speed for 2g Experience in a Rotating Machine

    Homework Statement A NASA astronaut is placed in a rotating machine to see how well their bodies withstand G Force. What rotational speed is needed in a device that has a 6.25 m radius to allow a 75.8 kg astronaut to experience a force that is twice his normal weight (or 2g)?Homework Equations...
  36. P

    Earth's Rotation & g-Force Effects

    if the Earth stops rotating , what will happen to the apparent value of g on its surface ?
  37. F

    Finding velocity from g-force?

    Okay so this is more of a theoretical question. If say a car crashed into a stationary truck and the driver experienced around 20-25g, what other factors would you need to find how fast the car was going before impact and how would you do that?
  38. X

    Calculating G-Force in Ski Jumping: 40m Radius, 37 to 9 Degrees

    Hello, I´m a skijumper and wondering the amount of g-forces I am put through in the innrun. So this is the data: Radius 40 meter Angel before the curve 37 degrees Angel after the curve 9 degrees Speed 93 km/h The speed at the start of the curve is probably 85 km/h and 93 km/h at the end...
  39. C

    G-Force and Water: Can Submersion Help?

    Greetings, Would submerging a human in water, such as by filling the cockpit, eliminate pressure from G force in a rocket launch? Thanks
  40. S

    Can someone edit my g-force paper

    Can someone edit my paper on g-force. I just need you to look for proper terminology usage and if anything needs clearing up. Also if you have any suggestions it'll be greatly appreciated http://rapidshare.com/files/424446844/Math_IA.docx
  41. 3

    Horsepower, Pounds and G-force

    If I know the vehicle weight in pounds and I know peak G-force. Can I find peak net horsepower? If yes, how would I do it? I have an accelerometer on my “Motor Driven Cycle” and I have weighed myself and the cycle. To keep the cycle legally a Motor Driven Cycle it must be under 5 bhp. If I...
  42. J

    G-force question. amusment park physics

    hey, i am a year 11 student trying to complete an assignmnt based on the physics in the amusment park 'dreamworld' i have been ask to change something about a ride and write about safety and thrill factor this would affect, a chose the giant drop ( a free fall ride ) i am planning to...
  43. M

    Horsepower to G-Force: Calculations for a Tetherball

    This question is for background information on a start up technology. Starting with the tetherball analogy: Assuming the force would be applied to spinning the base of the tetherball pole what amount of horse power is needed to get the tetherball up to a speed of 36 miles per hour with...
  44. C

    Exponential modeling of G-force

    Homework Statement Derive an equation of the form y=ax^b to model the given data: (35, 0.01) (28, 0.03) (20, 0.1) (15, 0.3) (11, 1) (9,3) (6, 10) (4.5, 30) Homework Equations Well, I know the answer is y = (7790 +/- 1246)x^(-3.698+/-0.1036) because that's what LoggerPro spits out, but...
  45. M

    G-Force Accelerometer conversion to Pounds per Square Inch

    So, the title says it all. background info on this question. I purchased a Herman Digital Trainer. It measure the impact of punches and kicks based on G-Forces. I was wondering if it was possible to a G-Force reading into Pounds per square inch reading. This is the websites description...
  46. S

    Understanding Shock Sensor G-Force Ranges & Outputs

    I have no experience with shock sensors and am looking for some insight. The ones I have found say a range in g's (example - range: 10,000g) and then give a maximum value. I was wondering if the range would be similar to a minimum that the sensor is able to read or how close to the given range I...
  47. J

    If I jump from height of 5ft to ground -what is g-force of impact

    I jump off a high bench (5ft high) to the ground. What is the g-force of the impact and how do you calculate it. It seems mass is irrelevant for this Joe
  48. S

    G-Force Measurement: Formulas for Launching into Orbit

    Hello folks, Does anyone know any formula about g-force measurement when launching into orbit? For example, 1 G at ground, 3-5 G during launching, 0 G at orbit. Thanks, Tim
  49. J

    Rocket launch that produces a certain g-force

    How do you calculate the period during rocket launch that produces a certain g-force? Is there a formula to work this out?